An international research group says it has made an important step toward practical quantum computing by implementing a full quantum algorithm without knowing its answer. Scientists from the University of Bristol and the University of Queensland led the group. The researchers implemented the phase estimation algorithm, a core central quantum algorithm that achieves an exponential speedup over all classical algorithms. “Unlike previous demonstrations, we built a full quantum circuit to implement the phase estimation algorithm without any simplification,” says project director Xiao-Qi Zhou. “We don’t need to know the answer in advance and it is the first time the answer is truly calculated by a quantum circuit with a quantum algorithm.” The project paves the way for important applications such as quantum simulations and quantum metrology in the near term and factoring in the long term, says professor Jeremy O’Brien, director of Bristol’s Center for Quantum Photonics. He says quantum algorithms eventually could facilitate the design of new materials, pharmaceuticals, or clean energy devices.